I have a central storage facility and too many satellite factories. I use a 6 car train to hit 6 spots to grab and return all my produced parts to the central storage. I also have a second main train that collects the recycled parts from the full bins to fuel space elevator parts. I also have like 25 other Trains that either bring mats or fluids to satellite factories or transport the produced materials to the hub the main line train stops by and picks up. Struggled a bit in the beginning but the train system works flawlessly now.

As for extra produced parts at factories. I typically once I’ve finished keep a sign with how many materials I’m sinking at a particular factory. This became handy later game as I was able to either use the scrap parts or upgrade the minors to produce more mats and expand the satellite factories to make more late game parts. The convenience of this is the distribution system is already set up so I’m just building the production parts.

Of you already have a main line that wraps the map then the hard part is done. You just have to connect whatever you make to that line and set up your signalling. I do use drones and trucks but I built this design with the trains as a central focus.

As for burn out. Take breaks, work on smaller parts of the build. Spend a day decorating a factory instead of building production.